Thanks for the info Ade
I have put it aside for a while too many projects but i will let you know how I get on.
One other thing that confused me is what controls the end float of the crankshaft. At the moment I can slide it across and back and the magnet can foul the ignition pick up. If I tighten the 6 screws more, that hold the casing together it stops the crank sliding but then its tight to turn?.